What is the acceptable reading on an explosimeter for safe tank entry?

In the context of safe tank entry, the correct reading on an explosimeter is 0% of the Lower Explosive Limit (LEL). This is crucial because the LEL indicates the minimum concentration of a flammable gas in the air that, when mixed with air, can ignite. A reading of 0% LEL signifies that there are no detectable flammable gases present in the atmosphere within the tank, thereby minimizing the risk of a hazardous situation.

When readings are at or above a certain percentage of LEL, it indicates the presence of flammable gases. For instance, readings at 1%, 5%, or even 10% of LEL pose increasing risks because the potential for explosion or fire starts to escalate as gas concentrations rise. Therefore, a reading of 0% LEL is essential for ensuring the safety of personnel entering the tank. It confirms an atmosphere that is free from the immediate risk of flammable gases. This is why a reading of zero is the only acceptable condition for safe tank entry.